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Enhancement of photovoltaic efficiency in CdSexTe1−x (where 0≤x≤1): Insights from density functional theory

journal contribution
posted on 10.12.2019 by Michael Watts, Tom Fiducia, Biplab Sanyal, Roger Smith, Michael Walls, Pooja Goddard
Recent advancements in CdTe photovoltaic eciency have come from selenium grading, which reduces the band gap and signicantly improves carrier lifetimes. In this work, density functional theory calculations were performed to understand the structural and electronic eects of Se alloying. Special quasirandom structures were used to simulate a random distribution of Se anions. Lattice parameters decrease lin- early as Se concentration increases in line with Vegard's Law. The simulated band gap bowing shows strong agreement with experimental values. Selenium, by itself does not introduce any defect states in the band gap and no signicant changes to band structure around the Γ point are found. Band oset values suggest a reduction of recombination across the CdSeTe/MgZnO interface at x 0:1875, which corresponds with the Se concentration used experimentally. Band structure analysis of two cases x=0.03125 and x=0.4375, shows a change from dominant Te/Se contributions in the conduction band minimum to Cd/Se contributions as Se concentration is increased, hinting at a change in optical transition characteristics. Further calculations of optical absorption spectra suggest a reduced transition probability particularly at higher energies, which conrms experimental predictions that Se passivates the non-radiative recombination centres.

Funding

EPSRC Supergen SuperSolar Hub (EP/J017361/1)

Swedish Research Council (grant no. 2017-05447

History

School

  • Science

Department

  • Chemistry
  • Mathematical Sciences

Published in

Journal of Physics: Condensed Matter

Volume

32

Issue

12

Publisher

IOP Publishing

Version

AM (Accepted Manuscript)

Rights holder

© IOP

Publisher statement

This is an author-created, un-copyedited version of an article published in Journal of Physics: Condensed Matter. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-648x/ab5bba

Acceptance date

26/11/2019

Publication date

2019-11-26

Copyright date

2019

ISSN

0953-8984

eISSN

1361-648X

Language

en

Location

England

Depositor

Dr Pooja Goddard Deposit date: 7 December 2019

Article number

125702

Exports